'Sherlock' Season 3 finale: Blackmail and something about Mary in 'His Final Vow'

"Sherlock" really knows how to end a season.From the first moments of the Season 3 finale, "His Final Vow" -- set in a crack-house -- to the final twist 90 minutes later, there were few dull moments in the quick-moving, violent plot. Also, the good guys basically won in the end. That's always fun.Watson is bored againA month or so into married bliss, and John Watson is bored again. We're talking about the kind of bored that results in combat-filled dreams and casual trips to crack dens with a tire iron in the pocket. Fortunately for John, Mary is supportive of all of this.Less fortunate is the fact that the newlyweds haven't been seeing much of Sherlock Holmes over the previous few weeks.Imagine Watson's surprise when he meets up with Sherlock in the very same crack-house he has just infiltrated in order to find a neighbor's teenage son.It's not what it seems ... Not...